One- to two-week trips: For business travelers or those who prefer to check luggage, a backpack, wheeled suitcase, or duffel bag of about 4,000 cubic inches should suffice in most cases. If you can pack light, opt for travel luggage that meets the criteria for carry-on bags, and avoid the hassle and fees of checked luggage.

A month or more: For extended travel, you can find wheeled suitcases with a capacity of 5,000 cubic inches, or backpacks with carrying capacity up to 5,500 cubic inches. If you need even more space, look for wheeled duffel bags that can hold 8,000 cubic inches.